Basically, the existing injection pile driver uses a combination of two mechanisms; a vertical driving actuator that is used in conjunction with either a side gripping holder, top gripping holder or just simply pressing down on the pile's top surface.
In the prior arts such as WO93/01364 and U.S. Pat. No. 6,368,023B1, the pile driver employs one or more vertical hydraulic jacks mounted on frames with large dead weights of more than 50 to 1000 tons to be moved on tracks or slide on hydraulic footsteps. This kind of machines is disadvantageous and clearly cannot be moved to work in confined spaces like in a basement of a building.
In U.S. Pat. No. 7,300,230B2 and EP2006070165, as the pile driver that does not use the side gripping mechanism, it will considerably reduce the ability to drive long piles. This driving mechanism will require a tall frame with a rigid horizontal member to support the jack to thrust the ram downwards on to the top of the pile. Using this method is obviously disadvantageous because the pile length will be limited to the clear distance taken from the tip of the hydraulic ram to the top of the existing driven pile in the ground, and moreover only short pile can be driven to avoid buckling.
In U.S. Pat. No. 6,368,023B1, as a modification to increase the driven length of pile without the side gripping mechanism, it uses two drive heads with a frame structure in two driving stages but nevertheless the frame structure will take up some vertical space in a limited room head and is unable to drive a high capacity and maximum continuous length of underpinning pile (62) at least equal to the clear floor height of a building.
In U.S. Pat. No. 5,433,556 and U.S. Pat. No. 2,204,283, a simply pressing down on the pile's top surface requires that the foundation has to be excavated and jacked against the base of the foundation to the top of the pile that is being driven; clearly this is cumbersome, difficult and can only drive many small pile lengths.
U.S. Pat. No. 5,722,798 and U.S. Pat. No. 4,925,345 has disadvantages in the loading method even though using a side gripping mechanism as it requires that the pile be slotted vertically from the top into an opening of a fixed horizontal thrust member which is located some height above the ground, therefore reducing the maximum possible pile length to be driven. Similarly, in U.S. Pat. No. 5,135,335 the twin pile gripping assembly is the obstructing member.
EP2006070165, U.S. Pat. No. 5,722,798 and U.S. Pat. No. 4,925,345 use pile gripping mechanism for driving small pile by means of employing wedges to jam the driving pile is difficult, slow and unable to prevent a total slippage. In another case, U.S. Pat. No. 5,135,335 and U.S. Pat. No. 4,411,408 employ slots in the pile to be used as gripping mechanism, but these slots will be difficult to fabricate in full section such as concrete square pile as it may initiate crack formations.
EP1806455A1 uses top hydraulic clamps in the pull and push method as commonly used in driving sheet piles in a row, however since these pile gripping mechanism is applied from the top of the piles it is therefore unable to drive maximum pile length.
The pile drivers mentioned in the above prior arts have drawbacks such as having either tall frame, heavy and bulky structure or inconvenient top loading of pile which is difficult to mobilise into a small confined space with limited head room and drive the pile at or below the foundation sub-structure. Therefore, the present invention has overcome these disadvantages.